Heat exchanger, particularly for use as a rack evaporator in refrigerators or freezers

Abstract: Heat exchanger, including a plurality of stacked shelves (2) and comprising for each shelf: a coil (3), constituted by a tubular body extending along a path with bends alternated with straight and substantially mutually co-planar portions and by a supporting and/or heat-exchange enhancement structure (4) constituted by metal rods welded to the coil and forming, above the coil (3), a supporting surface which is substantially parallel to the plane of arrangement of the coil. The coil (3) has, for each shelf (2), at least one portion (7) that is disconnected from the supporting and/or heat-exchange enhancement structure (4), and this portion lies substantially parallel to the longer straight portions of the coil (3) and proximate to one side of the shelf (2). This portion (7) disconnected from the supporting and/or heat-exchange enhancement structure (4) is connected to a tubular portion (6) that mutually connects the coils of two shelves which are not mutually co-planar.

Description: The present invention relates to a heat exchanger, particularly for use as a rack evaporator in refrigerators or freezers. Refrigerators are known which are constituted by a box-like structure inside which a plurality of mutually stacked and spaced shelves is arranged to support the goods to be preserved. In order to achieve higher efficiency of the refrigeration circuit and to keep the temperature inside the refrigerator or freezer as uniform as possible, in some types of refrigerator each shelf is constituted by a coil evaporator formed by means of a tubular body extending along a path that forms bends alternated with straight and substantially mutually co-planar portions. A structure is furthermore associated with the coil of each shelf and may be constituted by rods welded to the coils or by a plate-like element which is seamed or rigidly connected (for example by welding or glueing or other known rigid coupling methods) to the associated coil and has the purpose of forming a supporting surface for the products to be arranged on the shelves and, at the same time, of increasing the heat exchange surface of the coil. In many kinds of these evaporators, indeed termed rack evaporators, the coils of the various shelves are formed by means of one or more tubular bodies which are variously folded so as to form the straight portions and the bends of each coil and mutually connect the coils of the various shelves. During the manufacture of the entire evaporator and/or during surface treatment and/or handling, transport and packaging, it is sometimes necessary to apply an axial torsion to some appropriate straight portions of the tubular body, and in particular to one or both of the outermost portions of the set of parallel co-planar tube portions that forms, together with the bends, the coil of the individual shelf (this set is hereafter simply termed "grid"). This possibility exists, and is sometimes used, in the tubular system of evaporators in which the supporting and/or heat-exchange enhancement surface is constituted by a plate which is seamed to the grid (rotation by axial torsion of the tube inside the seams), whereas in the evaporator, in which the supporting and/or heat-exchange enhancement surface is constituted by metal rods welded to the grid that constitutes the individual shelf, this possibility has never been available, since the rods have always been welded or otherwise rigidly coupled to all of the above mentioned tube portions: the required angle of axial torsion is in fact usually such that it does not allow to discharge the entire torsion onto the small portion of tube that has no welds to the rods and is in any case such as to cause unacceptable deformations on the rods and/or deformations/breakages of the tube portion affected by the rotation. In some types of rack evaporator there is an additional branch which is arranged proximate to one side of the shelf, is orientated at right angles to the longer straight portions of the coil, and is not affected by the supporting structure constituted by the rods. Although this solution at least partially solves the problem of torsion on the additional branch, it has the drawback that it greatly complicates the production of the evaporator, indeed due to the arrangement of the additional branch, and for this reason it can be adopted with some benefit only in the manufacture of evaporators having at the most two shelves formed with a single curved tube, thus forcing to mutually connect multiple pairs of shelves by welding. A rack evaporator having the features of the preamble of claim 1, is known from the document GB-A-2 008 733. The aim of the present invention is to solve the problems described above by providing a heat exchanger, particularly for use as a rack evaporator in refrigerators or freezers, in which it is possible to perform the desired torsion of the tube portion or portions of the various coils to obtain the stacked configuration of the various shelves without discharging stresses onto the rod structure rigidly associated with the coils. Within the scope of this aim, an object of the invention is to provide a heat exchanger, particularly for use as a rack evaporator, that can be obtained with limited production times and/or costs with respect to the production times required by conventional rack evaporators, whether manufactured with multiple separate and subsequently assembled shelves or with multiple shelves obtained from a single continuous tube. Another object of the invention is to provide a heat exchanger particularly for use as a rack evaporator which can have a lower defect rate and thus better general quality with respect to known evaporators. With this aim, as well as these and other objects in view, which will become apparent hereinafter, there is provided, according to the present invention, a heat exchanger, with features as set forth in claim 1. Further advantages of the heat exchanger according to the present invention will become apparent from the following detailed description of two preferred but not exclusive embodiments thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figure 1 is a view of the heat exchanger according to the invention in a first embodiment, laid out on a plane; figure 2 is a perspective view of the heat exchanger of figure 1, in the arrangement with stacked shelves; figure 3 is a perspective view of a shelf of the heat exchanger of the preceding figures; figure 4 is a view of the heat exchanger according to the invention in a second embodiment, laid out on a plane; figure 5 is a perspective view of the heat exchanger of figure 4 in the arrangement with stacked shelves; figures 6 to 8 are enlarged sectional views of some examples of the connection of a supporting and/or heat-exchange enhancement structure made of rods to the tubular bodies of the coil. With reference to the above figures, the heat exchanger according to the present invention, generally designated by the reference numerals 1 and 1a in the two illustrated embodiments, is composed of a plurality of stacked shelves 2, 2a and comprises, for each shelf 2, 2a, a coil 3, 3a to which a supporting and/or heat-exchange enhancement structure 4, 4a is connected; said supporting and/or heat-exchange enhancement structure is constituted by a plurality of parallel rods that are associated by welding to the various branches of the coil 3, 3a, and forms a supporting surface which is parallel to the plane of arrangement of the associated coil. More particularly, each coil, which forms one of the shelves of the exchanger, is preferably constituted by a single tubular body extending along a path with bends alternated with straight and mutually parallel and substantially co-planar portions. Both in the first and in the second embodiments, the coil 3, 3a of each shelf is contained within an ideal rectangle, and the longer straight portions of the coil are arranged parallel to two opposite sides of this ideal rectangle. The coils of the various shelves 2, 2a are mutually connected by a tubular portion 6, 6a, and the branch 7, 7a which is connected to this portion 6, 6a and lies substantially parallel and proximate to one side of the shelf and is disconnected from the supporting structure 4, 4a. More particularly, in both of the illustrated embodiments, there are two branches 7, 7a that are disconnected from the supporting structure 4, 4a and are arranged at two mutually opposite and parallel sides of each shelf. The two branches 7, 7a that are disconnected from the supporting structure 4, 4a are furthermore parallel to the longer straight portions of the coil in a same shelf, and their distance from the closest longer straight portion is preferably less than the distance between the various longer straight portions of the coil that are rigidly connected to the supporting structure 4, 4a. It should be noted that the expression "disconnected from the supporting structure" is to be understood as meaning that the branches 7, 7a are not rigidly connected to the supporting structure 4, 4a. This condition can be provided by the fact that the branches 7, 7a are not affected at all by the supporting structure 4, 4a, as shown in particular in figures 1 to 5, but also by the fact that the rods composing the structure 4, 4a are simply curled or bent or kept in contact with the branches 7, 7a, as shown in detail in figures 6 to 8, without thereby preventing torsional rotation of the branch 7, 7a with respect to these rods. In practice there is no rigid connection between the rods forming the supporting structure 4, 4a and the branches 7, 7a. By virtue of this fact, it is possible to manufacture the heat exchanger according to the invention by bending a single tubular body, forming the various coils 3, 3a and the connecting portion 6, 6a on a same plane and subsequently applying, by welding or glueing, the supporting and/or heat-exchange enhancement structure 4, 4a. Then, by bending the portions 6, 6a with respect to the coils constituting the various shelves of the evaporator, the various coils are stacked. It should be noted that the bending of the portions 6, 6a that mutually connect the various coils can produce stresses that discharge onto the branches 7, 7a of the coils which are thus disconnected from the supporting structure 4, 4a. In this manner, the stresses that discharge onto the branches 7, 7a are not transmitted to the supporting structure 4, 4a, which preserves its planarity without problems, and the connection of the supporting structure to the coil is unaffected. In practice it has been observed that the heat exchanger according to the invention fully achieves the intended aim, since the effects of the bending of the tubular portion that mutually connects the coils of the various shelves does not alter the shape and connection of the supporting structure applied to the coils in the various shelves. A further advantage is that the bending operations to stack the various coils that form the shelves of the heat exchanger are considerably simplified. Although the heat exchanger according to the invention has been conceived particularly for use as a rack evaporator, it can also be used as a simple heat exchanger, with the various coils arranged in planes having any orientation according to the requirements. In practice, the materials employed, so long as they are compatible with the specific use, as well as the dimensions, may be any according to the requirements and the state of the art. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: Heat exchanger, particularly for use as a rack evaporator in refrigerators or freezers, of the type composed of a plurality of stacked shelves (2,2a) and comprising for each shelf: a coil (3,3a), constituted by a tubular body extending along a path with bends alternated with straight and substantially mutually co-planar portions and by a supporting and/or heat-exchange enhancement structure (4,4a) constituted by metal rods welded to said coil (3,3a) and forming, above said coil, a supporting surface which is substantially parallel to the plane of arrangement of the coil, said coil (3,3a) having, for each shelf (2,2a), at least one portion (7,7a) that is disconnected from said supporting and/or heat-exchange enhancement structure (4,4a), said portion disconnected from the supporting structure being connected to a tubular portion (6, 6a) that mutually connects the coils (3,3a) of two shelves (4,4a) which are not mutually co-planar characterized in that said at least one portion (7, 7a) constitutes a coil branch that lies substantially parallel to the longer straight portions of the coil (3,3a) and proximate to one side of the shelf (2,2a), so that torsion stresses which are produced upon bending of said portions (6, 6a) that mutually connect the coils for constituting said stacked shelves of the evaporator, are discharged on said at least one disconnected portion (7, 7a) without being transmitted to said structure (4, 4a). Heat exchanger according to claim 1, characterized in that said coil (3,3a) lies, for each shelf (2,2a), within an ideal rectangle in which the longer straight sides are substantially parallel to two opposite sides of said rectangle, two portions (7,7a) of the coil (3,3a) being disconnected from said supporting structure (4,4a) and being arranged at said two opposite sides of said ideal rectangle. Heat exchanger according to the preceding claims, characterized in that the set of coils (3,3a) is formed by means of a single curved tubular body. Heat exchanger according to one or more of the preceding claims, characterized in that the distance of said portions (7,7a) disconnected from said supporting structure (4,4a) from the closest parallel straight portion of the coil is less than the distances between two of the other contiguous longer straight portions. Heat exchanger according to one or more of the preceding claims, characterized in that two portions (7, 7a) which are disconnected from the supporting structure (4, 4a) are provided, said portions (7, 7a) being arranged at two mutually opposite and parallel sides of each shelf (2, 2a). Heat exchanger according to one or more of the preceding claims, characterized in that the rods composing said structure (4, 4a) are curled or bent or kept in contact with said portions (7, 7a) lying parallel to said longer straight portions of said coils (3, 3a), so that there is no rigid connection between the rods and said portions (7, 7a) to prevent torsional rotation of said portion (7, 7a) with respect to said rods. Process for manufacturing heat exchangers, particularly for use as rack evaporators in refrigerators or freezers, consisting in: forming, by bending a tubular body, at least two coils (3, 3a), said tubular body extending along a path with bends alternated with straight and mutually parallel and substantially co-planar portions forming branches of said coils, said coils (3, 3a) forming each a shelf (2, 2a) of the exchanger and being arranged side by side on a same plane and being mutually joined by a tubular portion (6, 6a) of said tubular body; connecting a supporting and/or heat-exchange enhancing structure (4, 4a) constituted by metal rods to each of said coils (3, 3a), said supporting structure (4, 4a) being fixed to the branches of said coils (3, 3a) except for the branches of the coils joined to the tubular portions (6, 6a) that connects two mutually contiguous coils (3, 3a), the branches joined to said tubular portions (6, 6a) thus forming disconnected portions (7, 7a) lying substantially parallel to the longer straight portions of the coil (3,3a) and proximate to one side of the shelf (2,2a); bending the connecting portions (6, 6a) with respect to the coils (3, 3a) so as to stack the various coils forming the shelves (2, 2a) of the exchanger, the torsion stresses which are produced by said bending being discharged on said at least one disconnected portion (7, 7a), said stresses being not transmitted to said structure (4, 4a).

Inventors: LOCATELLI GIANBATTISTA, LOCATELLI, GIANBATTISTA
Applicants: ITALIANA CONDENSER SRL, CONDENSER ITALIANA S.R.L.
Application year: 1994
Main classification: F25B39
IPC codes: F28F1, F25D25, F25B39